The need for automotive air hoses having improved resistance to the high temperatures experienced in an engine compartment has been exacerbated by an increase in the number of parts and fixtures restricting the available space in automotive engine compartments. Many of these additional engine components are designed to satisfy the emissions regulations of various governmental authorities. Adding to the problem has been the need to reduce the wall thickness of automotive air in order to enhance resistance to negative pressure, a problem experienced in efforts to reduce the weight and size of automobiles.
Traditionally, materials such as chloroprene rubber (CR) and epichlorohydrin rubber (ECO) have been employed in the manufacture of bellows-type rubber hoses for use in automobiles. These materials have proved unsatisfactory in meeting the requirements of contemporary automotive engine compartments. CR, for instance, exhibits poor resistance to heat and ozone, and its lack of rigidity does not make CR conductive to reductions in hose wall thickness for purposes of enhancing negative pressure resistance. ECO, on the other hand, has better resistance to heat than CR, but its insubstantial rigidity is not amendable to necessary reductions in hose wall thickness. Additionally, ECO is considered to be an expensive polymer material by skilled artisans.
The present invention provides a composition possessing the following features: (1) exceptional heat and ozone resistance; (2) sufficient rigidity to permit reductions in hose wall thickness for purposes of enhancing resistance to negative pressure; and (3) limiting the impact on releasing characteristics when the present composition is molded. The compositions of the present invention are preferably used in the manufacture of bellows-type rubber hoses for use in automobiles.